The invention relates to a variably adjustable mechanical valve gear for at least one gas-reversing valve (1) provided with a closing spring (2) on a piston-type internal combustion engine having a drive mechanism (13) for generating a lifting movement that is effective counter to the force of the closing spring (2) on the gas-reversing valve (1) and with a stroke transfer means (4) in the form of a pivoting element (8), arranged between the driving mechanism (13) and the gas-reversing valve (1), which acts upon the gas-reversing valve (1) in the direction of its movement axis (14) and for which the lifting distance in the direction of the movement axis (14) can be changed via an adjustable guide element (11), wherein the pivoting element is connected to the gas-reversing valve with its end that is effective in the direction of the movement axis (14) and to the driving mechanism (13) with its end opposite the gas-reversing valve (1) and is guided to pivot back and forth on the guide element (11) designed as control curve (11.1).